Dodecanol monolayer

It was shown that the formation of 1-dodecanol adsorption layers is accompanied by inflection points in the surface pressure vi time plots, a feature characteristic to two-dimensional condensation. Also the compression of a spread 1-dodecanol monolayer leads to characteristic inflections in the surface pressure (fl) vs area per mole (or molecule) curves. The surface... 

Comparing the experimental IT-A isotherms with the theoretic models one can conclude that small aggregates are formed in 1-dodecanol monolayer, and this aggregation process precedes the formation of larger clusters. The same conclusion follows from the analysis of the dynamic surface pressure of the adsorbed monolayers [25]. 

For much bulkier surfactants the orderly arrangements observed for simpler surfactants appear to disappear. Johal et al. [43] used sum-frequency spectroscopy to observe the coadsorption of a series of trichain surfactants and dodecanol. Their data indicated that the best model for the coadsorption was one consisting of an ordered dodecanol monolayer with scattered monomers or small clusters of disordered trichain molecules. 

An alternative approach to producing a differently functional surface is to use spin coating techniques. This was done by Turner et al. [68], who spun cast layers of polystyrene onto a silica surface. They investigated the nature of the surface and of SDS adsorbed to that surface by neutron reflectivity and IR-ATR. A thin layer of polystyrene, 275 A, was established. The subsequent SDS adsorption was consistent with a monolayer 15 A thick and an adsorbed amount similar to that observed at the air-solution interface. Measurements above the cmc of SDS showed clearly the effects on the adsorption pattern of dodecanol impurities in the SDS. 

Table 3.2. Parameters of Volmer s model, Eqs. (3.12)-(3.14) for a spread monolayer of 1-dodecanol.

For the dodecanoic acid, in contrast to 1-dodecanol, the aggregation model yields a quite high aggregation number of n = 4, while no indications exist for the formation of larger clusters. Also, no data for spread dodecanoic acid monolayers could be found in literature which exhibit characteristic inflection points in the FI-A isotherm. The dependencies at 15-20°C usually correspond to the type of gaseous monolayers [34]. Therefore, a certain similarity exists in the behaviour of fatty acids and alcohols, i.e. for a smaller number of methylene groups the system... 

Funasaki and coworkers [12] studied intermolecular interactions in mixed micelle formation of polyoxyethylene (15) dihydrocholesterol (DHC-E015) with polyoxyethylene (7) dodecanol (C12E07), by means of volumetric methods. The objective of their study was to investigate the condensing effect of cholesterol on phospholipid monolayers and the membrane-thickening action of cholesterol on lecithin bilayers. The volume... 

Rigid films, such as those made from sodium dodecyl sulphate (S.D.S.), in the presence of dodecanol. The surfactant monolayers that border the liquid film are usually compact and rigid. Such rigid films can last very long (even for a year) if the evaporation is halted, e.g., in a closed container saturated with water vapor. 

The maximum adsorption = 1/slope (of linear plot) = 1/8300 = 0.00012 mol = 120.5 pmol g From the value corresponding to the monolayer, we can calculate the area occupied by each adsorbed dodecanol molecule using the equation ... 

The evaporation rate of water can be affected by placing a monolayer of an organic molecule such as dodecanol on the surface of the water. Explain. 

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